Conventionally, a device employing an electrophotographic system, for example an image forming apparatus such as a copier, a printer, and a facsimile, typically includes a rotatable photoconductor drum. In the device, a photoconductive layer of the photoconductor drum is uniformly charged, followed by being exposed to laser beams emitted from a laser scanning unit, to thereby form a latent electrostatic image on the photoconductor drum. The latent electrostatic image is developed with a toner, and then is transferred onto a transfer sheet serving as a recording material. The resulting transfer sheet is passed through a heat fixing device, to thereby thermally fix the image thereon. The device is equipped with a system for performing the aforementioned operations. As for a fixing system, generally, there has been employed a system, in which a toner deposited on a recording sheet is thermally softened and simultaneously pressed by passing the recording sheet between a fixing member for heating the toner (fixing roller or fixing belt) and a press roller that is in contact with the fixing member with pressure. In this fixing system, the toner image fused on the sheet is brought into contact with the fixing member, therefore, a material having excellent releasability (e.g., fluororesin) is formed into a layer with a thickness of 5 μm to 30 μm on the fixing member.
However, the fixing member used in the fixing system is locally abraded on regions of a fixing surface corresponding to edge portions (edge sides) of printing paper because numerous sheets of printing paper having the same width are conveyed on the same position relative to the fixing member. Accordingly, in the case of using printing paper having a wide width beyond the abraded portion, image quality is deteriorated, which is problematic. That is, when the fixing member is partially abraded, the abraded portion is not appropriately heated or pressured. Therefore, fixing failure may occur in the abraded portion or image failure may occur by transferring a shape of the abraded portion onto an image.
Recently, an elastic layer which has satisfactory elasticity is needed to be formed as an intermediate layer for the purpose of achieving fixability suitable for a color image, which is problematic in causing abrasion resistance to be significantly lowered.
In order to solve the above problem, as a means for improving abrasion resistance of the releasing layer, it has been known that filler such as inorganic filler is added to a fluorine-containing material which constitutes the releasing layer (see, for example, PTL 1). However, in this method, a molten toner is deposited on the inorganic filler portion to thereby significantly deteriorate releasability. In addition, the releasing layer is greatly increased in hardness, which deteriorates image quality. These problems are especially significant in a color image. In the case of the inorganic filler, the effect of improving abrasion resistance is deteriorated over time due to exfoliation of the filler. Further, the exfoliated filler may act as abrasive to promote abrasion.